The cause of sleepy legs at night is venous valve insufficiency in the lower extremities, a condition in which the valve function is not closed due to congenital factors or acquired factors such as prolonged standing and sitting. The valve is a structure within the veins of the lower limbs, equivalent to a small one-way open valve, which opens when blood flows back from the foot to the heart and closes when it refluxes toward the foot. However, if the valve has broken down, there will be blood in the process of return flow to the heart, from the valve reflux part into the vein, then the pressure in the vein will increase, and because of the increased pressure, the permeability of the vein will increase, resulting in fluid leakage from the vein to accumulate in the tissue interstices, so at night because of the lower extremity activities for a longer time and leg soreness and discomfort, sleepy feeling.